1. Field of the Invention
The present invention relates to a system for inserting a deformable intraocular lens into the eye. Examples of such a deformable intraocular lens include a deformable intraocular lens that is inserted into the eye in place of the natural lens when the later is physically extracted because of cataracts, and a vision correction lens that is inserted into the eye for the sole purpose of vision correction.
2. Description of the Related Art
In general, during cataract surgery, an intraocular lens is inserted into the eye, from which the natural lens has been removed (lens-removed eye), such that the intraocular lens is located in the original position previously occupied by the natural lens and restores vision. Various studies on the material and shape of such an intraocular lens have been carried out since Ridley performed the first implantation of an artificial lens in 1949.
In recent years, in addition to studies on intraocular lenses which are used for vision restoration after cataract surgery, intense studies on intraocular lenses for refractivity correction have been ongoing. Such an intraocular lens for refractivity correction is inserted into the eye which still has a natural lens (lens-carrying eye), for correction of nearsightedness or farsightedness.
In relation to cataract surgery, a technique for crushing the lens tissue by means of ultrasonic emulsification and suctioning the crushed tissue away has been popularized. This technique enables performance of lens removal surgery to excise an opaque lens through a small incision. Along with progress in the operational technique itself, intraocular lenses themselves have recently been improved. Such an improved intraocular lens is disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 58-146346. In the intraocular lens, the optical portion is made of a deformable elastic material. The intraocular lens is inserted, in a folded state, into the eye through a small incision and restored to its original shape within the eye allowing it to exert its proper lens function.
Accompanying these technical developments, the material of the optical portion of such an intraocular lens has been changed gradually from hard polymethyl methacrylate (PMMA) to silicone or soft acrylic resin, which enables the intraocular lens to be inserted into the eye in a folded state.
Moreover, in recent years, studies have been conducted on copolymers such as hydroxyethyl methacrylate and methyl methacrylate, as well as on hydrophilic materials such as 2-hydroxyethyl methacrylate (HEMA).
Further, intraocular lenses of different shapes have been studied and put into practical use, including an intraocular lens having a circular optical portion and loop-shaped support portions formed of different materials, an intraocular lens whose loop-shaped support portions and optical portion are formed of the same material, and an intraocular lens having plate-shaped support portions.
Furthermore, the following patent publications disclose insertion devices for inserting the above-described deformable intraocular lens into the eye in a compressed or folded state.
(1) Japanese Patent Application Laid-Open (kokai) No. 5-103803 discloses a device designed such that a holding member which holds a folded lens is attached to a main body, and the lens is inserted into the eye through an insertion tube provided at the tip end of the holding member.
(2) Japanese Patent Application Laid-Open (kokai) No. 7-23991 discloses a disposable insertion device for one-time use in which a portion for holding a folded lens is integrated with a main body of the device and the entirety of the device is formed of resin.
(3) Japanese Kohyo (PCT) Patent Publication No. 9-506285 discloses an intraocular-lens insertion device having a broadened range of applications. In the intraocular-lens insertion device, a lens is held in a stress-free state in an intermediate preparation region of a main body. After attachment of a cannulae (insertion tube) to the main body, the intraocular lens is inserted into the eye through the cannulae. The intermediate region serves as a lens package.
The conventional intraocular-lens insertion devices described in (1) and (2) above have the following drawbacks. When either of these devices is used, an intraocular lens removed from a package is placed on a placement portion of the device, is deformed, and then inserted into the eye. Therefore, during actual operation, work for placing the intraocular lens onto the device is needed, resulting in increased time and labor involved in implantation of the intraocular lens.
Further, such an intraocular lens and insertion device must be made germ-free through a sterilization procedure, because they are inserted into the eye through an incision. However, if an operator accidentally drops the lens and/or the insertion device onto an unclean surface, such as a floor or table, during the placement operation, the germ-free state is lost, and the lens and/or the insertion device become unusable.
Further, when the operator forcedly inserts into the eye an intraocular lens which has been placed on the device improperly, the lens may be broken, or may forcible fly out from the insertion tube, potentially resulting in damage to the internal tissue of the eye.
The intraocular-lens insertion device described in (3) above has the following drawbacks. Although the intermediate region of the device can be used as a lens package, work for attaching a cannulae (insertion tube) to the main body must be performed during actual use, because the cannulae (insertion tube) is a member which is formed separately from the main body. Although a technique for storing in advance an intraocular lens at the intermediate region located on the center axis of a push rod, the intermediate region is difficult to be formed from a material suitable for storing the lens. In addition, the intermediate region cannot be formed to have a function necessary for properly holding an intraocular lens having loop-shaped support portions. That is, although such an intraocular lens must be stored in a state in which the angle between the optical portion and the support portions of the intraocular lens is maintained, the intermediate region of the conventional insertion device cannot provide such an angle maintaining function.